Parking spaces and/or driveways often include a barrier or bollard so as to selectively bar entrance of vehicles to the parking space or driveway. Typically, such barriers may be controlled remotely, for example from within a vehicle, and move from one stable position to another stable position when a suitable command is received via a signal from the remote control source.
For a parking barrier to be effective, it must offer resistance against external forces that may try to push the barrier down to facilitate unauthorized access to the parking space. Numerous ways have been suggested for providing such resistance, however most of them result in excessive power loss or wear of the motor and parts of the barrier, making them inefficient, particularly when the barrier is battery operated.
While the barrier needs to offer resistance to external forces, it also needs to yield to excessive forces else the barrier and its mounting may become irrevocably damaged. It is known in the art that barriers can be provided with a defense against physical abuse. Some such defense mechanisms include the use of external compression springs as structural elements of a barrier, the use of internal compression springs disposed within the barrier and driven by a cam, or the use of a friction clutch. However, each of these mechanisms suffers from at least one crucial disadvantage.
External compression springs bend in a large radius, such that if a vehicle forces its way over the barrier, the barrier and/or the undercarriage of the vehicle are likely to be damaged. Cam driven defenses cause excessive friction. Such friction resists rotation when the defense returns the barrier to its blocking position, and reduces the torque available for raising the barrier, often leaving the barrier in an interim position between the blocking position and an open position. Friction clutches, which may be included in some defense mechanisms, present their largest resistance when first pushed, but drop the resistance level as the friction coefficient changes from static to dynamic. As such, once the friction clutch starts to yield, it can readily be pushed all the way to the ground.
For example, in PCT Patent Application Publication WO 2009/019171 to Ducati, a motor driven barrier including a worm gear is disposed between the motor and the barrier shaft, thus preventing the barrier from being forced from its upright position. However, the disclosed worm gear is inherently inefficient and causes a significant loss of the power, which highly degrades the lifetime of the battery in a battery operated system.
Further, U.S. Pat. No. 4,535,974 to Conde discloses use of external compression springs as structural elements of a barrier, such that the springs form the upright section of the barrier. When impacted, the springs bend and yield, and return to their original position when the external force is removed.
There is thus a long felt need in the art for a barrier system that provides a defense against physical abuse, which defense is self-sufficient, offers increasing resistance as the barrier is pushed down, reliably returns the barrier to its blocking position, and does not require use of battery power to return the barrier to the blocking position.